An RJ45 connector includes eight electrical connection pins and a domestic installation is in general wired using cable having four pairs of wires, each wire being connected to a respective pin of the RJ45 connector.
An RJ45 socket thus connected is considered. The four pairs enable access to several services on this same RJ45 socket. These services are:                an analog telephone service,        an IP (Internet Protocol) telephone service,        two Ethernet accesses.        
Adaptors have therefore been proposed to allow access to two services simultaneously from a single RJ45 socket. These adaptors include an RJ45 plug that can be connected to the RJ45 socket, and two RJ45 sockets. The internal wiring of the adaptors depends on the services to which they provide access.
It is to be noted that the analog and IP telephone services each use one pair of wires and that the Ethernet accesses each use two pairs of wires.
It is understood that to simultaneously use two different services, they must use different pairs, otherwise malfunctions would occur.
Thus, a first type of adaptor provides for the simultaneous use of an analog and an IP telephone service, using the third and fourth pairs.
A second type of adaptor provides for the simultaneous use of an analog telephone service and an Ethernet access using the first, second and third pairs.
A third type of adaptor provides for the simultaneous use of an IP telephone service and an Ethernet access using the first, second and fourth pairs.
A fourth type of adaptor provides for the simultaneous use of two Ethernet accesses using the four pairs.
These adaptors are designed and wired to provide for only connections or combinations of connections which function, according to the pairs used by each service. However, the user must use a different adaptor for each combination of services used simultaneously.